Highly directional steerable antennae for communication with earth satellites are required for such applications as communications for ships, aircraft and vehicles. While many designs exist to steer antennae, a particular antenna pointing problem exists in steering such antennae when carried by aircraft. This problem results from the aircraft flying high above the earth, resulting in the antennae having to point in a direction having a downward component in some circumstances, such as when the aircraft is banking, or when the aircraft is to communicate with another which is at a lower elevation, in contrast to earth-bound vehicles in which the antennae need be steered over an angle not exceeding 180.degree. , and usually over a much smaller angle.
Particularly when carried by an aircraft, the effect on the antenna of vibration and externally applied forces from any angle can affect the pointing direction of the antenna due to the effects of play and bending caused by angular momentum on the elements of the antenna. This can have severe consequences. For example, when an aircraft is experiencing turbulence and when a small highly directional antenna carried by it is locked onto a satellite for transmission or reception of communication data, antenna lock-on to the satellite can be lost. A similar problem can be experienced when the antenna is being carried at sea and a boat carrying it experiences rough water, or by a terrestrial vehicle being driven over a rough (e.g. washboard or pot-holed and/or mountainous) road. In such cases antenna driving motors continuously work to move the antenna and orient it to constantly point at the satellite. A momentum-induced deflection of the antenna can cause it to unlock from the satellite from a position which the driving computers would expect to be a correct position, and which would thus cause a complete reinitialization scan to occur. This is time consuming and maintains an undesirable broken communications condition during the scan.
Patents which describe antenna orienting mechanisms all of which suffer from the aforenoted problems are as follows: U.S. Pat. Nos. 4,454,515, 4,980,697, 5,091,733, 4,251,819, 4,379,297, Canadian Patents 1,223,340, 1,165,435 and Canadian patent publication 2,005,426.